Model Railway Viaduct
(A Work In Progress)
What is a viaduct?
viaduct is a bridge consisting of a series of spans or arches
that is used to carry a railway / railroad, or road over a
wide valley. In terms of a railway viaduct these are usually
built to join two areas of equal height to allow the railway to
remain level and thus to allow for the fast running of trains.
Where as it is easy for a train to turn left or right it is not
easy for a train to go up or down. Trains can only cope with a
gradual gradient change. This is why railways often meander
through the countryside following the contours of the land as
well as avoiding natural obstacles like rivers. The Great
Western Railway probably the most famous railway in the world,
built buy Isambard Kingdom Brunel was given the nickname the
"Great Way Round" due to the fact that it's routes were not the
most direct because they followed the contours of the land
giving the railway the most level and smooth ride possible. It
is a testament to how level and smooth the railway line was that
today it can carry HST's at 125mph without modification to the
When it is not possible to follow the contours such as across
areas with hills and valleys, the railway builders used a
technique called cut and fill were you cut out a some of the
hill to lower the level of the track bed and then use the fill
to build up the level of the track bed in the valley. Where this
was not an option they then had to turn to constructed
embankments, bridges and in the deepest and longest valleys,
Viaducts. Likewise with hills they first dug cuttings then
cuttings with supported sides and then for the biggest hills
they built tunnels to go through them.
My reason for building a railway
The modular layout I choose to build required a removable
section of tract to allow entry and exit from the inner circle
of the layout when not in use. My decision was to construct a
thin board to carry two running tracks across the gap in my
layout. Once constructed it immediately came to mind that it was
the perfect shape to be turned into a bridge.
The reason I choose a viaduct bridge was because it fit the
shape and size of the bridge and by using a viaduct rather than
a more modern design of bridge I would not date the layout thus
allowing me to run steam and modern diesel and electric trains
without them looking out of place.
also had access to a brick pattern and by using this it would
tie the bridge into the tunnel portals which will also be
covered with the same brick pattern.
Railway Viaduct Resources
For more pictures visit Railway Pictures at
www.railwaypictures.co.uk and search for viaduct
Brick Pattern used:
(brick pattern was resized)
How to build a Model Railway
x printed sheets of brick pattern.
x A1 size 1mm mounting card.
Note: (It is
assumed that you have already built a board to carry the track
bed. Below gives instructions for decorating this board to look
like a viaduct).
You can also build the viaduct out of ply, mdf etc, but I choose
card to keep the weight down.
scissors, craft knife, cutting mat, metal rule, a round plate or
other round item, pencil and pegs.
The first stage was to measure and cut out the sides of the
viaduct. For this I used the 1mm mounting card which I measured
and drew on the shape I wanted for the viaduct. There are so
many different designs that you have a lot of freedom in your
choice. I worked out I could have 4 arches on my bridge
The arches were never intended to go down much further than the
point at which the aches stop and the abutments start as I will
need to crawl underneath it when I am running the layout to get
in and out. Thus the viaduct is more of a representation of the
top of one.
arches are 22cm across and have abutments that are 4 cm wide. I
have also allowed 2cm above the track bed to act as a wall for
the top of the viaduct.
Once you have cut out both of your viaduct sides you will need
to fix them (I used PVA) to your track bed making sure the
arches are opposite to each other and that they are spaced an
equal distance from each other (square). In my case I also had
to make sure the wall at the top of the viaduct is the same
height across the length of the bridge. Once the glue has dried
you can start strengthening the structure.
make the viaducts arches strong and ridged I decided to glue
pieces of card between the two railway viaducts legs. I laid the
bridge on it's side, inserted the glued sections of card making
sure the viaducts sides remained square and straight. I then
placed weights on top of each leg until the PVA glue dried. Once
dried this created a very strong and ridged structure.
To build the sides and roof of the arches I
first needed to measure the distance between each viaduct side.
I then added 1cm each side which will be used as a gluing
surface to hold the arch in place. I came to the conclusion that
I would only build part of the arches as I needed some where to
hold on to when I need to remove the viaduct section of board
from the layout.
After you have cut out the section of arch
wall I scored down both sides 1cm in from the edge and then bent
the card over to make a right angle. I then put slits into the
extra bit of card that was bent over, to allow the card to
follow the curve in the bridge. These extra tabs that I had
created are to allow me to glue the viaducts walls in place (see
I then glued the side wall in place following
the curve in the viaducts arch wall (see pictures below). To
hold this in place I used some small clamps (I also used pegs).
This process was repeated seven times more
until all the arches had side walls. As you can see from the
pictures shown below you will need a lot of clamps or pegs.
The next step was to cover the viaduct with a
decorative covering of brick or stone (various colours). I
choose to use the brick pattern, which is available in the
download section, to cover the viaduct in a red / blue brick
colour and pattern. It was a simple process of cutting away any
of the white paper left after printing and then gluing the
sheets onto the viaducts sides with a thin layer of PVA glue
(see picture below).
Each sheet was large enough to fit across the
arch and after a few minutes of drying I cut out the centre of
the arch leaving a 1cm overlap. I then cut slits in the 1cm
overlap and like I did with the arch sides, I folded these over
and glued them to the inside of the arch. This left a nice
curved shape to the arch and will allow for some overlap in the
brick pattern between the viaducts sides and the inside of the
arch (see pictures below).
Once you have covered both sides in the brick
pattern you can move onto the inside of the arches. Firstly you
will need to cut the brick pattern paper to the correct width.
When cutting you can leave some overlap at the top and bottom as
you can use the excess to wrap around the end of the card which
will help secure the brick pattern further. When you are happy
with the size of the brick pattern paper you can glue it down
The last step is to glue some more brick pattern
paper to the inside walls of the viaduct either side of the
And your done.